A projection display device includes a light source system, an illumination optical system, and a projection optical system. “System” refers to a group or mechanism in which individual elements function as a whole while interacting with each other. The light source system emits projection light. The illumination optical system guides the light emitted from the light source system to a light valve. The light valve outputs image light in accordance with an image signal. The projection optical system magnifies and projects the image light onto a screen. Here, “image light” refers to light having image information. “Light valve” refers to an optical shutter that controls transmission or reflection of light. The light valve is, for example, a liquid crystal panel or a digital micro-device (DMD; registered trademark). Conventional mainstream light source systems use pressure mercury lamps or xenon lamps as light sources. Recently, projection display devices using light emitting diodes (LEDs), laser diodes (LDs) (referred to below as lasers), or other light sources are being developed.
In light source systems using LEDs or lasers, since an individual light source is poor in brightness compared to a lamp, it is necessary to use multiple light sources to enhance brightness. For example, Patent Document 1 discloses a projection display device that uses a dichroic mirror to combine lights emitted from multiple LEDs and converge them on the same position of an incident surface of a rod integrator (referred to below as a light intensity equalizing element). Patent Document 2 discloses a projection display device that uses a right-angle prism and a composite rod integrator to combine lights emitted from multiple light sources.